Homogeneous propellant compositions of lithium perchlorate and polylactam



3,107,185 HOMGGENEQUS PRQPELLANT CQMPGSI- TIGNS 9F LlTl'llUh l EERQHL'JRATE AND PGLYLACTAM Ross M. Hedrick and Edward H. Mottus, Dayton, Ghio, assign'ors to Monsanto Chemical Company, t. Louis, Mo., a corporation of Belaware No Drawing. Filed Mar. 6, 1958, Ser. No. 719,593 27 (Zlaims. {CL 149-2) This invention relates to novel compositions of matter which are useful as solid rocket propellants and to the process of preparing same. More specifically this invention relates to compositions of matter comprising a lactam polymer and lithium perchlorate and to the process of preparing same, including blending of a polylactam with lithium perchlorate and cast-polymerization of a lactam in the presence of the lithium perchlorate.

Liquid compositions as the fuel-oxidant mixture for rockets present serious problems. The use of liquid propellants require considerable plumbing, valves, metering pumps and intricate controls to provide the means for effecting delivery of the fuel and oxidant to the combustion chamber in the proper ratio. The liquids employed are extremely corrosive and are also subject to loss. Therefore, rockets employing liquid propellant compositions are not reliable for long standing in readyto-go-condition. Furthermore, handling the corrosive liquids is a hazardous, time-consuming and cumbersome job, which precludes their use in tactical weapon systems in the field and aboard ships.

In contradistinction thereto the solid propellant motor is inherently very simple since the ratio and distribution of fuel, oxidant and additives are fixed when the solid propellant is prepared. Thus the solid propellant system requires no plumbing, valves, or controls and contains no mechanical moving parts which can go wrong. The solid propellant rocket also generally is characterized by relatively long storage life, ease in handling and high reliability, such that it is in constant readiness for instant use, whereby it is well adapted for tactical and strategic weapon systems in field use and aboard ships. A further advantage of the solid propellant rocket is that the relatively rigid propellant charge aids in the support of the chamber during handling and when in use such that a lighter-weight case can be employed, which saving in weight plus the elimination of much hardware required for a liquid propellant system provides a bigger pay-load.

Conventional composite solid propellant compositions generally consist of an inorganic oxidant and a plastic binder, winch also serves as the reductant-fuel of the system. The aforesaid system is a heterogeneous composition wherein the burning rate and stability to detonation are dependent to some extent upon the particle size of the oxidant. Both of these properties are improved as the particle size of the oxidant is reduced, but milling to provide a finely divided oxidant is hazardous and periodic explosions are encountered.

The principal object of this invention is to provide an improved solid propellant composition. Another object of this invention is to provide an improved process for casting solid propellant compositions in rocket cases. Still another object of this invention is to provide a novel solid propellant composition having a high specific impulse. A further object of this invention is to provide a novel solidpropellant composition which is homogeneous. A still further object of this invention is to provide a novel solid propellant composition characterized by improved stability to shock. Other objects and advantages of this invention will be apparent to those skilled in the art from the following disclosure.

It has now been found that lithium perchlorate and BAWJSE Fatented Got. 15, 1963 2 the polylactams, wherein the lactam monomer for the said polylactam contains from 5 to 7 members, i.e. from 4 to 6 carbon atoms, in the lactam ring, are mutually soluble and the combination thereof is a homogeneous composition. The presence of the lithium perchlorate renders the polylactam non-crystalline such that the polylactam is in a rubbery, amorphous state, which is tougher than the crystalline polylactam. The aforesaid mutual solubility also is present between the lithium perchlorate and the lactam monomers, e.g., pyrrolidone, piperidone, and e-caprolactam, such that said monomers can be polymerized in the presence of the lithium perchlorate to provide solid homogeneous compositions thereof.

The system lithium perchlorate-polycaprolactam can be employed to further illustrate this invention. Thus, lithium perchlorate is soluble in polycaprolactam and in the monomer e-caprolactam, whereby a homogeneous composite composition is obtained. The lithium perchlorate-polycaprolactam composition can be prepared by blending the two components together at temperatures preferably from about C. to about 250 C. in suitable mixers, extruders, or on a mill roll and the like. The blending operation preferably should be carried out with as little agitation as possible to preclude entrapment of gas in the composition, which would generally require a degassing operation under vacuum. Another method of preparing the lithium perchlorate-polycaprolactam composition is to dissolve the lithium perchlorate in ts-caprolactam and add a base catalyst or a catalystpromoter system, as hereinafter more fully described, whereby the fluid composition can be introduced into any desired container and polymerized in place. The lithium perchlorate-polycaprolactam composition can also be readily extruded for use in relatively small-bore projectiles.

The preferred relatively low temperature, base-catalyzed, N,N-diacyl-initiated polymerization process is disclosed in the copending US. application Serial No. 627,- 934, filed December 13, 1956, now US. Patent No. 3,017,391, issued January 16, 1962, of which this application is a continuation-in-part.

Ellective base catalysts are the alkali and alkaline earth metal catalysts, which are elfective either in the metallic form or in the form of hydrides, borohydrides, oxides, hydroxides, carbonate, amides, etc. Lithium and sodium hydrides are particularly preferred catalysts in the composition of the present invention. The base catalyst is employed in an amount of from about 0.05 percent up to about 5 percent, and preferably from about 0.1 percent up to about 1 percent by weight of the lactam present in the composition.

The N,N-diacyl compounds suitable as promoters can be selected from the class of compounds containing the essential active group:

wherein N is a tertiary nitrogen atom (i.e., has no hydrogen atoms attached thereto), A is an acyl radical selected from and B is an acyl radical selected from and R is a third substituent of the same kind of general type as A or B; or a hydrocarbyl radical such as aryl,

alkyl, aralkyl, alkaryl, cycloalkyl, etc; or a heterocyclic radical such as pyridyl, quinolyl, etc. or any of the afore-' mentioned groups substituted with or containing additional radicals or groups such as carbonyl, N-substituted carbamyl, alkoxy, ether, sulfonyl, tertiary amino, etc.; or any other non-interfering groups, i.e., groups which will not preferentially react with thelactam or which will not otherwise interfere with the essential effective activity of the polymerization catalyst.

The substituents attached to the carbonyhthiocarhonyl and sulfonyl radicals A and B are unlimited, provided they are free from interfering groups (e.g., primary amino groups or strong acid functions which will interfere with the alkali or alkaline metal catalysts). Examples of noninterfering groups are hydrogen atoms, as Well as hydrocarbyl and heterocyclic radicals mentioned in the preceding paragraph, including such radicals substituted with or containing polar-substituents such as tertiary amino, acylamido, N-substituted carbamido, ether, etc. The radicals A and B can be attached together to form a ring system (e.g., the cyclic irnides described in greater detail below). Likewise, the radical A and the tertiary nitrogen atom can constitute a part of a ring system not including the radical B (e.g., the lactams described below).

A preferred class of materials having the aforementioned structure are N-substituted imides, i.e., compounds of the foregoing type having at least two acyl groups attached directly to the tertiary nitrogen atom. This group of compounds can be represened by the following structural formula:

in -(L A particularly effective class of N-substituted imides are the N-acyl lactams such as N-acetyl-Z-pyrrolidone, N-acetyl-e-caprolactam, N-benzoyl-e-caprolactam, N-ben zoyl-6-valerolactam, N-ethylcarbamyl-e-caprolactarn, N- propionyl-w-caprylolactam, N-toloyl-w-decanolactam, etc.

Another preferred class of N-substituted imides' comprise the cyclic imides of dicarboxylic acids. Examples Examples of other N-substituted imides suitable forthe above-described improved polymerization are N,N- diacetylmethylamine, N,N-dibenzoylaniline, triacetamide, N-acetyl-N-formyl ethylamine, N-propionylsaccharin, etc.

Another general class of compounds useful for the polymerization process comprise the N-acylsulfonamides containing no hydrogen atom on the sulfonamide nitrogen atom. Examples of this general class of materials are -N-acetyl-N-ethyl-p-toluene-sulfonamide, N-ethyl-N-lauroylethanesulfonamide, N,N-diacetylmethanesulfonamide, N-(phenylsulfo'nyl)succinimide, N-methylsaccharin, N- acetylsaccharin, N acetyl-N methylbenzenesulfonamide and numerous other N-acyl sulfonamides.

Another class of suitable compounds for the polymerization process comprise the disulfonamides such as V N,N-di-(p-toluenesulfonyl)anilide, N,N-di-(benzenesulfonyl)methylamine, and other N,N-dibenzenesulfonyl alkylamines, as Well as the corresponding N,N-dialkanesulfonylalkylamines such as N,N-di-(methanesulfonyl)-ethylamine, etc.

. Another general type of effective promoter compounds N-nitrosuccinimide, N,N-diacetylnitrosamine, N-nitroso- N-acetyl-propylamine, N-nitroso N,N-di-n-butylurea,

Representative members i N-methyl-N-nitrosourethane and other N-substituted N- nitroso-carbamates, etc.

7 Another general class of promoters for the polymerization process comprises the N-nitrososulfonamides, such as N-nitroso-N-methyl-benzenesulfonamide, N-nitroso-N- methyl-p-toluenesulfonamide, N-nitroso-N-ethyl-methanesulfouamide, N-nitroso-N-phenethyl-butanesulfonamide, etc.

As was indicated above, one or more of the acyl oxgen atoms of the various compounds described herein can be substituted with sulfur atoms to form the corresponding thioacyl compounds without destroying the effectiveness of such compounds as promoters for the polymerization of the lactams. Examples of such thio compounds are l-acetyl-Z-thiohydantoin and 3-butyl-5,5-dimethyl-2- thio-2,4-oxazolidinedione. Other suitable thio analogs of the foregoing acyl compounds are N-thiobenzoyl-2- .pyrrolidone, N-thiopropionylmaleimide, N-phenyldithiosuccinimide, N-(n-octylcarbamyl)-2-thiopyrrolidone, etc. To preclude the presence of large inert groups in the above-described N,N-diacyl promoters it is preferred that the'molecular weight of the compound does not exceed about 1000' and more about 500.

The process can be carried out at a temperature up to about 250 C. and preferably where the catalyst-promoter system is employed at temperatures up to about 190 C. and more preferably between about C. to about C. for the polymerization of e-caprolactam in the presence of major amounts of lithium perchlorate and down to about 35 C. for the lower molecular weight lactams, e.g., pyrrolidone.

The amount of N,N-diacyl promoter employed in the polymerization process can vary from about 0.01 to about 5 mole percent of the lactam monomer and Will preferably vary from about 0.01 to about 2 mole percent, and more preferably still from about 0.1 to 1 mole percent, the lower concentrations being used when a higher molecular weight polymer is desired.

preferably still does not exceed When the solid propellant is produced by extrusion for insertion in small-bore rocket cases a small amount of the catalyzed-promoter system liquid polymer composition can first be added to the cylinder case such that the insertion of the extruded mass will displace the liquid polymer forcing it to rise in the annular space between the extrusion mass and the cylinder wall whereby the inserted mass is securely bonded within the case. The

liquid polymer can .be of similar composition to the has solidifiedprovliding the desired internal cavity to effect proper radial burning of the propellant.

In general the weight ratio of thelithiurn perchlorate to the polylactam. will vary from about 2:1 to about 4: ludepending on the particular polylactam employed and the various additives which may be incorporated therein. For example, the weight ratio of the lithium perchlorate -.to polycaprolactam should preferably be about 2.5:1 to oxidize the polycaprolactam according to the following equation: a

8(C H ON) -|-21LiClO V V V Where more energy may be desired by oxidation of the carbon monoxide to carbon dioxide, up to 33 moles of the lithium perchlorate can be employed, i.e., up to about 3.875 parts by weight of lithium perchlorate per part of polycaprolactam. It will be understood that the presence of other additives may alter the aforesaid weight ratios.

The composite system lithium perchlorate-polycaprolac-tam for the weight ratio 2.47:1 was found to have a specific impulse of the order of about 250 sec. or higher at 1000 psi. chamber pressure. In addition to this desirable relatively high specific impulse the system is also extremely valuable in that it also possesses a high volume impulse value. The combination of these two desirable properties makes the composite solid rocket propellants of this invention particularly valuable in high performance applications.

Also the novel lithium perchlorate-polyl aotam compositions of this invention can contain various other components finely dispersed therein such as the finely divided light metals and various hydrides thereof, e.g., beryllium, boron, magnesium, aluminum, magnesium hydride, aluminum hydride, the various solid hydrides of boron such as decaborane, alkylated deoabor-anes (ethyl alkylated decabonane), aluminum borohy-dride, and the like. For example, the composite system lithium perchlorate-polycaprolactam for the weight ratio 2.47:1 may preferably contain up to about 20 percent by weight of the total composition of atomized aluminum (particle size about 20 microns). Preferably the aforesaid materials should be sufficiently fine to all pass a standard 100-mesh screen, and more preferably should pass a ZOO-mesh screen.

These light metal and metal hydride high-energy additives should preferably not exceed about 25 weight percent of the total composition. Notwithstanding the relatively high-energy content per unit of weight of the aforesaid additive-s, the heavy combustion exhaust tends to lower the performanw of the solid propellant composition such that it is often desirable to incorporate not more than from 5 to about weight percent of said additive, based on the total weight of the propellant composition.

Another class of additives which can be incorporated in the lithium perchlorate-polylactam compositions are the relatively low molecular weight plasticizers, for example, the sulfonamides such as N-monosubstituted toluenesulfon-amides, e.-g. N-e-thyl-p-toluenesulfonarnide, N-ethyl-otoluenesulfon-amide and mixtures thereof; disubstituted amides such as dimethyl formamide; and glycol ethers such as triethylene glycol dirnethyl ether; butyrolactone; ethylene glycol; and the like. The fairly polar plasticizers preferably should also be solvents for the lithium perchlorate such that the components of the system are mutually soluble or dispersible to effect a homogeneous solid composition. The presence of the plasticizcr in the noncrystalline polylactam renders the composition more rubbery and provides a material improvement in the tensile elongation of the material. These composite compositions are characterized by their ability to provide a good seal between the solid propellant and the rocket motor case, which insures proper radial burning of the propellant without overheating the rocket motor case. The plasticizer employed also functions as a fuel element in the composite solid propellant and the ratio of the lithium perchlorate is adjusted such that a proper balance is maintained between the oxidant and the fuel combinations to provide complete combustion. The amount of plasticizer employed can vary up to about 35 weight percent of the polylactam present in the composition, but amounts of from about to about weight percent are generally preferred.

The lithium perchlorate-polylactam compositions of the invention are useful as a solid propellant for rockets including shout-range ballistic weapons, such as aircraft and artillery rockets, and long-range strategic missiles, wherein they may be the sole pro-pellmt or be employed ignited. They are also exceptionally stable to shock and heat. Thus it was demonstrated that small pieces of the lithium perchloratepolycaprolactam composition could be hammered repeatedly on a steel anvil without detonation. Excellent thermal stability was demonstrated by heating a sample of the aforesaid composition at 300 C. for 2.5 hours without ignition.

The following examples are illustrative of this invention:

Example 1 A mixture of 2.5 parts by weight of lithium perchlorate per part by weight of polycaprolactam was prepared by blending in a ball mill. Then the mixture was heated to a temperature of 190 C. and the two components melted down to give a transparent viscous material. The cooled material was a tough and horny product which appeared very homogeneous. On ignition the product burned vigorously with a smooth continuous flame.

Example 2 Example 3 A mixture of lithium perchlorate, polycaprolactam and aluminum powder was heated together in a weight ratio of 625:l25:212, respectively, at 240 C. A paste was formed at this temperature and on cooling a hard, cement- -like product was obtained. This product burned easily on ignition.

Example 4 A mixture of lithium perchlorate, polycaprolactam andv magnesium hydride was heated together in a weight ratio of 625::227, respectively, at 240 C. Upon cooling a white cement-like material was obtained. The product burned very smoothly on ignition.

Example 5 Example 6 One part by Weight of caprolactam was added to 2.5 parts by weight of anhydrous lithium perchlorate at a temperature of about 180 C. and the mixture was stirred to aid the solution of the perchlorate in the monomer. Then 0.012 part by weight of N-acetyl caprolactam and 0.05 part by weight of a 3 molar solution of phenyl magnesium bromide were added to the mixture and stirred to effect a uniform distribution of the initiator and catalyst in the said mixture. It was noted that there was an increase in viscosity of the system within three minutes. The composition was held at about 180 C. for a time of about 3 hours and then cooled. The homogeneous homogeneous composition was easily stirrable.

' 7 lithium perchlorate polycaprolactam composition was easily ignited with a flame and burned vigorously and smoothly.

Example 7 A composite blend was prepared by heating together 2.5 parts by weight of lithium perchlorate, 0.8 part by Weight of polycaprolactam, and 0.2 part by Weight of :triethylene glycol dimethyl ether at 240 C. The fluid, After cooling it was found that this composite composition had considerable elasticity and fibers prepared therefrom could be easily stretched more than 100 percent before breaking.

Example 8 A composite blend was prepared by heating together 3.33 parts by weight oilithium perchlorate, 1 part by weight of polycaprolactarn, and 0.44 part by weight of ethylene glycol to a temperature of 220 C. until a homogeneous composition was obtained. Then the composite blend was cooled and found to be a rubbery composition which could be stretched and deformed and rolled or reformed into new shapes. This composite blend burned vigorously and smoothly when ignited.

Example 9 A composite blend was prepared by heating together 2.5 parts by Weight of lithium perchlorate, 0.75 part by weig t of polycaprolactarn, and 0.34 part by weight of butyrolactone to a temperature of 220 C. with stirring to efiect a homogeneous melt. cooled to room temperature and found to be'a leathery product which burned vigorously and smoothly when ignited.

The molecular weight of the polylactam should preferably be above about 10,000 and below about 75,000 to enable proper blending with the lithium perchlorate and other additives. A particularly desirable range of molecular weight of the polylactam for this purpose-is from about 10,000 to about 40,000. t wiil be understood that when the case-polymerization system is employed the molecular weight of the polymer in the composite is of less-importance, but must of course be sufficiently high to provide a solid composite composition under temperatures to which the material may be exposed prior to firing. Accordingly, a molecular weight of at least about 10,000 should be effected in the cast-polymerization proc ess-of preparing composite compositions for solid rocket propellants.

We claim:

1. A composition of matter consisting essentially of a substantially homogeneous solid solution of lithium perchlorate and a polylaotam in a weight ratio of from about 2:1 to about 4:1, wherein the lactam monomer for the said polylactam contains from 4 to 6 carbon atoms in the lactam ring.

2. A composition of matter consisting essentially of a homogeneous solid solution of lithium perchlorate and a polyl'actam in a weight ratio of from about 2:1 to about 4:1 and the said polylactam is obtained by the polymerization of lactams defined by the structural formula:

and polycaprolactam' in a weight ratio of from about 2:1 to about4zl.

The composition was 5. The composition of matter of claim 4,'wherein the weight ratio is about 2.5 1.

6. A composition or" substantially homogeneous solid solution of lithium perchlorate and a polylactam in a weight ratio of from about 2:1 to about 4:1, wherein the lactam monomer for the said polylactam contains from 4 to 6 carbon atoms in the lactam ring, and uniformly dispersed therein up to about 25 percent, by weight of the total composition, of a high-energy additive selected from the group consisting of beryllium, boron, magnesium, aluminum, :maghesium hydride, aluminum hydride, aluminum borohydride, decaborane, alkylated decaborane, and mixtures thereof.

7. A composition of matter consisting essentially of a substantially homogeneous solid solution of lithium perchlorate and polycaproiactam in a Weight ratio of from about 2:1 to about 4:1, and uniformly dispersed therein up to about 25 percent, by weight of the total composition of a high-energy additive selected from the group consisting of beryllium, boron, magnesium, aluminum, magnesium hydride, aluminum hydride, aluminum borohydride, decaborane, alkylated decaborane, and mixtures thereof.

8. The process of preparing a substantially homogeneous composition of lithium perchlorate and a polylactam, wherein the lactam monomer for the said polylactam contains from 4 to 6 carbon atoms in the lactam ring, comprising heating a mixture of lithium perchlorate and a polylactarn in a weight ratio 'of from about 2:1 to about 4:1 to a temperature up to about 250 C. until a substantially homogeneous solution is obtained and thereafter casting the fluid composition and allowing it to solidify. g

9. The process of claim 8, wherein the polylactam is polycaprolactam and the temperature employed is from about 150 C. to about 250 C.

10. The process of preparing a substantially homogeneous composition of lithium perchlorate and a polyla-ctam comprising the polymerization of lactam monomer containing from 4 to 6 carbon atoms in the lacta-m ring in the presence of from about 2 to about 4 parts by weight of anhydrous lithium perchlorate, per part by weight of monomer, and effecting polymerization of said monomer by the presence of a base-catalyst in the amount of from about 0.05 to about 5 weight percent, based on the monomer, and from about 0.01 to about 5 mole percent, based on the monomer, of an N,N-diacyl promoter compound having a tertiary nitrogen atom and having at least two of the three N-substituents selected from the group con- I of from about 0.1 to about 1 mole percent.

12. The process of claim 11, wherein the monomer is e-ca'prolactam. V

13, The process of claim 12, wherein the polymerization process is carried out at a temperature below about C.

14. The process of claim 13, wherein the base-catalyst is sodium hydride and the promoter is N-acetyl capr'olactam. I r

15. The process of claim 13, wherein the base-catalyst is lithium hydride and the lactam.

16. The process of claim 13, wherein the lithium p erchlorate is present in a weight ratio of about 2.5 times that of the caprolactam.

17.'The process of claim 11, wherein the monomer is pyrrolidone. V p

18. The process of preparing a solid rocket propellant comprising the processof claim 10, wherein up to 25 per-,-

cent, by weight of the total composition, of a high-energy matter consisting essentially of a promoter is N-acetyl capro additive selected from the group consisting of beryllium, boron, magnesium, aluminum, magnesium hydride, aluminum hydride, aluminum borohydride, decaborane, alkylated decaborane, and mixtures thereof is uniformly dispersed therein in a finely divided form and maintained in a substantially uniform dispersion by mild agitation until the polymer is advanced to a viscosity which reains said group of metals and hydrides thereof in a substantially uniform dispersion and thereafter completing the polymerization of the monomer at a temperature below about 190 C.

19. The process of claim 18, wherein the monomer is e-caprolactam.

20. The composition of matter of claim 1 having uniformly dispersed therein in a finely divided form a minor amount of aluminum.

21. The composition of matter of claim 1 having uniformly dispersed therein in a finely divided form a minor amount of 'boron.

22. The composition of matter of claim 1 having uniformly dispersed therein in a finely divided form a minor amount of magnesium.

23. The composition of matter of claim 1 having uniformly dispersed therein in a finely divided form a minor amount of magnesium hydride.

24. The process of preparing a solid rocket propellant composition comprising the process of claim 10, wherein up to 25 percent, by weight of the total composition, of finely divided aluminum is uniformly dispersed therein and maintained in a substantially uniform dispersion by mild agitation until the polylactam is advanced to a viscosity which retains the powdered aluminum in a substantially uniform dispersion and thereafter completing the polymerization of the monomer at a temperature below about 190 C.

25. The process of preparing a solid rocket propellant composition comprising the process of claim 10, wherein up to 25 percent, by weight of the total composition, of finely divided boron is uniformly dispersed therein and maintained in a substantially uniform dispersion by mild agitation until the polylactam is advanced to a viscosity 10 which retains the powdered boron in a substantially uniform dispersion and thereafter completing the polymerization of the monomer at a temperature below about C.

26. The process of preparing a solid rocket propellant composition comprising the process of claim 10, wherein up to 25 percent, by weight of the total composition, of finely divided magnesium is uniformly dispersed therein and maintained in a susbtantially uniform dispersion by mild agitation until the polylactam is advanced to a vis cosity which retains the powdered magnesium in a substantially uniform dispersion and thereafter completing the polymerization of the monomer at a temperature below about 190 C.

27. The process of preparing a solid rocket propellant composition comprising the process of claim 10, wherein up to 25 percent, by weight of the total composition, of finely divided magnesium hydride is uniformly dispersed therein and maintained in a substantially uniform dispersion by mild agitation until the polylactam is advanced to a viscosity which retains the powdered magnesium hydride in a substantially uniform dispersion and thereafter completing the polymerization of the monomer at a temperature below about 190 C.

References Cited in the file of this patent UNITED STATES PATENTS 2,479,470 Carr Aug. 16, 1949 2,539,404 Crutchfield Jan. 30, 1951 2,563,265 Parsons Aug. 7, 1951 2,780,996 Hirsch Feb. 12, 1957 2,783,138 Parsons Feb. 26,1957 2,855,372 Jenkins et al. Oct. 7, 1958 OTHER REFERENCES Chem. and Eng. News, May 27, 1957, pp. 18-23.

Chem. and Eng. News, January 6, 1958, pp. 79-81.

Arendalez' Industrial and Eng. Chemistry, vol. 48, No. 4, April 1956, pp. 725-6.

Deschere: Industrial and Eng. Chemistry, vol. 49, No. 9, September 1957, pp. 1336-6. 

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF A SUBSTANTIALLY HOMOGENEOUS SOLID SOLUTION OF LITHIUM PERCHLORATE AND A POLYLACTAM IN WEIGHT RATIO OF FROM ABOUT 2:1 TO ABOUT 4:1, WHEREIN THE LACTAM MONOMER FOR THE SAID POLYLACTAM CONTAINS FROM 4 TO 6 CARBON ATOMS IN THE LACTAM RING. 